complex project, need advices

yes but someone told me there's a way to mod the boards or something.

Possibly.

Looking over this thread, I think you'll struggle to achieve what you want to do. How good are you at programming? This is not a trivial sketch to write.

well, i'll try to see what i can do .. and tell you you were right i guess, but i'll try.

I don't know if you've seen this: x0xb0x®: Transistorize the World

It might give you some pointers.

thanks, it seems to be really a cool project. But my project is more simple than that sequencer i think.

recording a midi message ( 24 first messages from the midi info received, or less ) , then playing it back, note after note, same spacing between each note.
Then controls for each note, by two options : global velocity for all notes , and global note lenght for all notes. And the second option combined : individual controls for each note ( velocity, lenght ) .
Then, while the sequence is being played in the midi out, the machine can receive a key information by the midi in, to transpose the whole sequence to this note height. that's the base. It might start to be messy when several notes would be played at the same time, so the machine would perhaps have troubles to know where to transpose the sequence.

the perfect example that shows what i'm describing is here at 2:17. See how he transposes the sequence.

then , some features to correct the info about which key it is, on each note. and which steps are blank, and at which step the sequence restarts from the begining, or the other option to have the sequence played only once, or twice, etc ..

Hope you are aware that there is gonna be a considerable latency in what you want to achieve...And i mean quite an audible one, mind !! It is already audible in much faster processing like PC's, nevermind in a uC like arduino !!

Plus auto quantizing is quite prone to misinterpretation, depending how accurate you can play( and we all know how hard it that, when opposed to quantized music, right ?!?) So, for live music , and cosidering you want to do it real time it seems you have a lot of obstacles to transpose there.

i don't understand why there would be a latency, other than when adjusting a controler, the time needed for the sample rate to be synchronised with the new information from the button you're turning.
other than that, it's like the blipping of the little led on the arduino board : if i set it to a desired frequency, like 100 ms off , 200 ms on , 50 ms off etc etc ... the difference is that it's in midi info, not led light. and each note of the synth/keyboard is a different led i'm playing with, one by one :
500 ms this note, with 90 of velocity, then
500 ms this other note, with 90 of velocity, then
500 ms this other note, with 120 of velocity , etc etc ...

But maybe i'm wrong somewhere ?

And what are you gonna base the clock reference on ?!? You gonna need a master clock( Word time clock, mtc ?!?) to base the calculation on, to start with am i right ?!?

yes off course, a tempo button that would adjust all the spacing between all the notes events, which are all the same in any case
An overal button to adjust proportionaly the velocitys of each notes ( though they can be adjusted independantly, so this button adjusts the values proportionaly, or with a reset button : to a default value that the global velocity button adjusts )

Otherwise wont be able to quantise, to start with. All it could do would be replay at same time you did, but then to find a right end of 4 beats/8 beats( depend on time signature) would be a bit of a guess ?!? and if you were able to overcome that, then whatever inconsistency you might have misplayed( cause you would do) it would be more and more noticeable as the track/loop keeps playing.
Sorry if i sound discouraging, but i am a just trying to find the logic in it and see if it works( which at the moment, i dont think it will just with the arduino, unless you have other peripherals connected to it in order to work).
Is it making sense to you ?!?
for what you aresaying you would be better off with a behringer controller like the BCF or BCR 2000 and a live performance sequencer /DAW like reason/ableton and a PC!! Cheap and 100% effective !

And im not on about the buttons you need but the BPM clock in which the code to base it self. Im assuming you d have a good knowledge of all the intricacies of MID and sequencing

no , you didn't understand.
Whatever speed i'm playing between each note, whatever unconsistency i'll have while playing, all the arduino has to understand when recording it is :
note 1 ... this ( E )
note 2 ... this ( A )
note 3 ... this ...

i'll ask him to play E, then A then etc , at his own contant speed that i'll adjust ( 500 ms between E, A , etc or 400 between all the notes, or 300 etc ... ) that's all.

pc sequencers and other stuffs are crap, and nothing like what i want. i tried that before ... and the sewuenders from cubase 5. crrraaaaaaap !! that's a pity.
lol, fuck reason, fuck abbleton ; ) ha ha ! they didn't understand what i'm looking for, much more simple.

much much more simple ^^

fair play; Problem is you mentioning it is not only to be used in real time, but also to then be looped. It will need something to base itself on, a time scale, right ?!? your note might be half way the measure you wanna use, might be 3/4, etc. Otherwise wont be able to loop it. Plus on a live performance we all know how much it varies throughout the track. Get me?!?
And if you saying that about the DAW's i mentioned, then u need to dig deeper into them. You are talking to a music producer , but also as a live musician .
Either you not getting what im saying, or im not explaining myself right ( which i think i did already).
Now if you tell me that your band plays live with a metronome( that can send a MTC to the arduino) then things are different

Where im getting is that is not as simple as you think it is... And cubase has come a long way. Maybe you need to catch up with all its new features. A lot of [people gave up on their 20 grand mixers and dozens of thousands of pounds just to trade it for a more digital based one. I still keep my fully analog based studio with a 48 channel mixer and 24 multitrack recorder just cause i love the analog stuff, plus im a dub head, otherwise i can tell u i would have done the same. I also have 20 channels in and 20 out of cubase( as a back up thing and for more digital genres, as i also compose for many artists) and know cubbase quite well.. What you saying, even live is so easy, with it. If you knew how hard it is to match a loop to a live performance, you would give up now or at least understand what im saying.
Now if you wanna do it for proof of concept, you will definitely need more than just an arduino, i can tell u that now !! Hands down !!
Sit down, do a block diagram of all things and how they will work ( might be easier to understand), and you will start realizing what im saying !!
without a time signature, there is no loop. At least not a workable one, as would be all over the place.
Record something, or use a live band track, and try to make a loop out of it....and note the time and how hard will be to do so !! Then let us know

no this isn't what you imagine, again. i didn't mention what you're describing.

i don't know how to say even more clearly. Whatever i'll play on the keyboard, once, will be recorded, but transformed. the only thing that will be recorded from the keyboard will be the each note height. that's all. then the arduino will play back each notes, each step, one by one, with the same spacing between each note. Is it more clear ?

then the tempo will be adjusted on the arduino by adjusting the spacing between each start of the notes played back. and the sequence played back is looped or not.

No no, all the stuffs i've seen or that you mentioned, all the softwares, none can do what i'm exactly looking for. i'm cloning the principle of the sequential pro one.

there's the doepfer sequencer, but to me it's crap. It adjusts the notes for each step, ok, but with a potentiometer. nothing comes from the keyboard. the soft versions i've seen propose some step sequencers or stuffs like that, but really not the interface i'm looking for, not fun at all, with the mouse etc ... quite close to the doepfer actualy.

look at the sequential pro one again, this is my quest, only in midi, to control an emu II or some other stuffs, on the run, after i set a cool sequence quickly. it's that simple :

the guy sets the sequencer to record what he's gonna play, whatever unconsistency he'll have, and then the pro one plays the sequence back, with a different constant, ( same lenght between each note recorded previously ) and also loops it if wanted. then the player hit a key and the sequence is transposed to this key. that's all. Not what you're describing or think i described.

another example, with an elka synthex i think, very 80'. imagine that the synth does da da da da da da da on the same note height , unless you transpose it, and here it is :

the machine works the sequence all by herself, all you're doing is transposing it with the same keyboard that has let you create the sequence that's being played. ( i'm not mentioning the mods applied to the sequence here again, but the main lines first )

And you're talking to a musician too, who builds vintage JTM45/100, blackflag, superleads, and guitars, basses, univibes, fuzz, octavia ... Echoplex repairs ..

no, i think you don't understand yet.
how did they play their sequential circuits back in the days ? how do they play the pro one in the first video i show you ? on the run, easy, that's all i'm looking for. you're saying it's impossible or something, but i won't use it the way you think i'll do. How do they use their pro one in the video, again ? just the way i intend to play it. so it's not impossible as you can see that with your eyes.
and they just hit a "loop" button so the machine loops it. i think you don't get it.
i dislike the sequencer versions offered on every softwares available.
+1 on the analog systems, and tape.

Where im getting is that is not as simple as you think it is... And cubase has come a long way. Maybe you need to catch up with all its new features. A lot of [people gave up on their 20 grand mixers and dozens of thousands of pounds just to trade it for a more digital based one. I still keep my fully analog based studio with a 48 channel mixer and 24 multitrack recorder just cause i love the analog stuff, plus im a dub head, otherwise i can tell u i would have done the same. I also have 20 channels in and 20 out of cubase( as a back up thing and for more digital genres, as i also compose for many artists) and know cubbase quite well.. What you saying, even live is so easy, with it. If you knew how hard it is to match a loop to a live performance, you would give up now or at least understand what im saying.
Now if you wanna do it for proof of concept, you will definitely need more than just an arduino, i can tell u that now !! Hands down !!
Sit down, do a block diagram of all things and how they will work ( might be easier to understand), and you will start realizing what im saying !!
without a time signature, there is no loop. At least not a workable one, as would be all over the place.
Record something, or use a live band track, and try to make a loop out of it....and note the time and how hard will be to do so !! Then let us know

look at tangerine dream, vangelis, or jan hammer ..
the way the machines were designed and limited by some aspects, almost invented the 80' style.
these days, we can do anything we want, but most that comes out is crap anyway. peoples don't understand.

You havent got the main issue/obstacle here... THE TIME SIGNATURE NEEDED for arduino know where to end the loop.Unless you make it in the arduino, use it to record those notes, and only then he can [process, quantize, and if requested change pitch( aka transpose), or increase/deecrease tempo.. Only that way would work just with arduino.

Even the old sequencers had a time signature(Ex a decade counter or other means)

Ah, wait- Are u refering to an arpegiator instead ?!? Cause that is what the video sounds like, each note triggered and the arpegiated to a time signature. If so, thats a whole kettle of fish.